JP7582887B2 - Current detection circuit, synchronous rectification type step-down DC/DC converter and its control circuit - Google Patents

Description

The present invention relates to current detection of low-side transistors.

Push-pull switching circuits containing high-side and low-side transistors are used in synchronous rectification step-down converters, inverter circuits for motor drive, and various power conversion devices.

To control a switching circuit or its load, it is necessary to monitor the current flowing through the switching circuit. Known current detection methods include inserting a sense resistor in the current path and detecting the voltage drop across the sense resistor, and detecting the voltage drop due to the on-resistance of the high-side transistor and low-side transistor.

JP 2012-39823 A

When a switching circuit operates in current source mode, it may be necessary to detect the current flowing through the low-side transistor. In current source mode, current flows in the reverse direction through the low-side transistor, which generates a negative voltage at the output node of the switching circuit, making it difficult to detect the current based on the on-resistance of the low-side transistor.

The present invention has been made in light of this situation, and one exemplary purpose of one aspect of the present invention is to provide a current detection circuit capable of detecting the current of a low-side transistor.

One aspect of the present disclosure is a current detection circuit. This current detection circuit is used with a push-pull switching circuit including a high-side transistor and a low-side transistor, and detects a source current flowing through the low-side transistor. The current detection circuit includes a capacitor, (i) a switch circuit that connects a first end of the capacitor to a ground line and a second end of the capacitor to a switching line to which the high-side transistor and the low-side transistor are connected in a first phase, and (ii) a switch circuit that makes the first end of the capacitor high impedance and connects the second end of the capacitor to the ground line in a second phase, and an output circuit that has a high impedance input and outputs a current detection signal based on the voltage generated at the first end of the capacitor in the second phase.

Another aspect of the present disclosure relates to a control circuit for a synchronous rectification type step-down DC/DC converter including a high-side transistor and a low-side transistor. The control circuit includes a current detection circuit that generates a current detection signal indicating a current flowing through the low-side transistor during a period when the low-side transistor is on, and a pulse modulator that generates a pulse signal for controlling the high-side transistor and the low-side transistor based on the current detection signal. The current detection circuit includes a capacitor, a switch circuit that (i) connects a first end of the capacitor to a ground line and connects a second end of the capacitor to a switching line to which the high-side transistor and the low-side transistor are connected in a first phase, and (ii) makes the first end of the capacitor high impedance and connects the second end of the capacitor to the ground line in a second phase, and an output circuit that has a high impedance input and outputs a current detection signal based on a voltage generated at the first end of the capacitor in the second phase.

In addition, any combination of the above components, or mutual substitution of the components or expressions of the present invention between methods, devices, systems, etc., are also valid aspects of the present invention.

According to one aspect of the present invention, the current of the low-side transistor can be detected.

FIG. 1 is a circuit diagram of a current detection circuit according to an embodiment. FIG. 2 is an equivalent circuit diagram of the current detection circuit in the first phase. FIG. 3 is an equivalent circuit diagram of the current detection circuit in the second phase. FIG. 4 is an operational waveform diagram of the current detection circuit of FIG. FIG. 5 is a circuit diagram of a configuration example of the switch circuit of FIG. FIG. 6 is a circuit diagram showing an example of the configuration of the output circuit. FIG. 7 is a circuit diagram of a DC/DC converter. FIG. 8 is a diagram illustrating an example of an electronic device including a DC/DC converter. FIG. 9 is a circuit diagram of the motor drive system.

(Overview of the embodiment)
A summary of some exemplary embodiments of the present disclosure will be described. This summary is intended to provide a simplified summary of some concepts of one or more embodiments for a basic understanding of the embodiments as a prelude to the detailed description that follows, and is not intended to limit the scope of the invention or disclosure. Furthermore, this summary is not an exhaustive summary of all possible embodiments, and is not intended to limit essential components of the embodiments. For convenience, the term "one embodiment" may be used to refer to one embodiment (example or variant) or multiple embodiments (examples or variants) disclosed in this specification.

A control circuit for a synchronous rectification type step-down DC/DC converter including a high-side transistor and a low-side transistor according to one embodiment includes a current detection circuit that generates a current detection signal indicating a current flowing through the low-side transistor while the low-side transistor is on, and a pulse modulator that generates a pulse signal for controlling the high-side transistor and the low-side transistor based on the current detection signal. The current detection circuit includes a capacitor, a switch circuit that (i) connects a first end of the capacitor to a ground line and a second end of the capacitor to a switching line to which the high-side transistor and the low-side transistor are connected in a first phase, and (ii) sets the first end of the capacitor to a high impedance and connects the second end of the capacitor to the ground line in a second phase, and an output circuit that has a high impedance input and outputs a current detection signal based on a voltage generated at the first end of the capacitor in the second phase.

With this configuration, by using a combination of a capacitor and a switch circuit, the voltage drop of the low-side transistor can be detected as a positive voltage, and a current detection signal based on the voltage drop can be generated.

In one embodiment, the switch circuit may include a first switch provided between the first end of the capacitor and the ground line and turned on in the first phase, a second switch provided between the second end of the capacitor and the switching line and turned on in the first phase, a third switch provided between the second end of the capacitor and the ground line and turned on in the second phase, and a fourth switch having one end connected to the first end of the capacitor and turned on in the second phase. With this configuration, a negative voltage generated on the switching line can be converted to a positive voltage.

In one embodiment, the output circuit may further include a voltage/current conversion circuit that converts the voltage generated at the first end of the capacitor in the second phase into a current signal. By converting it into a current signal, it becomes easier to add or subtract it from other signals in the downstream pulse modulator.

In one embodiment, the voltage/current conversion circuit may include a first transistor having a first end connected to a power supply line, a second transistor having a first end connected to the power supply line and a control terminal connected to the control terminal of the first transistor, a resistor provided between the second end of the first transistor and the ground line, and an operational amplifier that receives the voltage generated at the first end of the capacitor and the voltage at the second end of the first transistor and has an output node connected to the control terminal of the first transistor, and outputs a current flowing through the second transistor.

In one embodiment, the control circuit may be monolithically integrated on a single semiconductor substrate. "Monolithic integration" includes cases where all of the circuit components are formed on a semiconductor substrate, and cases where the main components of the circuit are monolithically integrated, and some resistors, capacitors, etc. may be provided outside the semiconductor substrate for adjusting the circuit constants. By integrating the circuit on a single chip, the circuit area can be reduced and the characteristics of the circuit elements can be kept uniform.

(Embodiment)
Hereinafter, the embodiments will be described with reference to the drawings. The same or equivalent components, parts, and processes shown in each drawing will be given the same reference numerals, and duplicated descriptions will be omitted as appropriate. In addition, the embodiments are not intended to limit the invention, but are merely examples, and all features and combinations thereof described in the embodiments are not necessarily essential to the invention.

In this specification, "a state in which component A is connected to component B" includes not only cases in which component A and component B are directly physically connected, but also cases in which component A and component B are indirectly connected via other components that do not substantially affect their electrical connection state or impair the function or effect achieved by their combination.

Similarly, "a state in which component C is provided between components A and B" includes not only cases in which components A and C, or components B and C, are directly connected, but also cases in which they are indirectly connected via other components that do not substantially affect their electrical connection state or impair the function or effect achieved by their combination.

FIG. 1 is a circuit diagram of a current detection circuit 300 according to an embodiment. The current detection circuit 300 is used together with a push-pull switching circuit 400 including a high-side transistor 402 and a low-side transistor 404. The high-side transistor 402 is provided between a power supply line (or an input voltage line) IN and a switching line SW, and the low-side transistor 404 is provided between the switching line SW and a ground line GND. The high-side transistor 402 and the low-side transistor 404 are driven by a driver circuit 410. An inductive element such as an inductor, a coil, or a reactor is connected to the switching line SW.

In an operation mode (called a current source mode) in which the output current _IOUT of the switching circuit 400 flows in the positive direction (to the right in the figure), a current _IH flows from the input line IN to the switching line SW during the on-period of the high-side transistor 402. At this time, the voltage of the switching line SW is
V _SW =V _IN -R _{ON_H} ×I _{H
R ON_H} is the on-resistance of the high-side transistor 402.

During the on-period of the low-side transistor 404, a current _IL flows from the ground line GND to the switching line SW, and the voltage of the switching line SW at this time is
V _SW =-R _{ON_L} ×I _{L
R ON_L} is the on-resistance of the low-side transistor 404.

The current detection circuit 300 detects a current _IL flowing through the low-side transistor 404, and outputs a current detection signal IS indicative of the current IL.

The current detection circuit 300 includes a capacitor C31, a switch circuit 310, and an output circuit 320.

The switch circuit 310 is connected to the capacitor C31, the switching line SW, and the ground line GND, and is configured to be able to switch between a first phase (sampling phase) φ1 and a second phase (hold phase) φ2. The first phase φ1 and the second phase φ2 are controlled by a controller (not shown).

(i) In the first phase φ1, the switch circuit 310 connects the first end n1 of the capacitor C31 to the ground line GND and connects the second end n2 of the capacitor C31 to the switching line SW.

In addition, (ii) in the second phase φ2, the switch circuit 310 sets the first end n1 of the capacitor C31 to high impedance and connects the second end n2 of the capacitor C31 to the ground line.

The switch circuit 310 can be configured with a combination of multiple switches, and the arrangement of the multiple switches is not particularly limited.

The output circuit 320 has a high impedance input, receives the voltage V _SNS generated at the first end n1 of the capacitor C31 in the second phase φ2, and outputs a current detection signal IS based on the voltage V _SNS at the first end n1. The current detection signal IS generated by the output circuit 320 may be a voltage signal, in which case the output circuit 320 may be a buffer (amplifier). The current detection signal IS may also be a current signal, in which case the output circuit 320 may be a voltage/current conversion circuit.

The above is the configuration of the current detection circuit 300. Next, the operation will be described. Figure 2 is an equivalent circuit diagram of the current detection circuit 300 in the first phase φ1. Figure 3 is an equivalent circuit diagram of the current detection circuit 300 in the second phase φ2.

2, in the first phase φ1, the first terminal n1 of the capacitor C31 is grounded, and the voltage V _SW of the switching line SW is applied to the second terminal n2 of the capacitor C31, so that the capacitor C31 is charged with the voltage V _SW .

3. In the subsequent second phase φ2, the second end n2 of the capacitor C31 is grounded, and the voltage V _n1 at the first end n1 is output as the detection voltage V _SNS to the output circuit 320 at the subsequent stage. The voltage V _n1 at the first end n1 is a voltage with the polarity of the switching voltage V _SW reversed, and is a positive voltage. The output circuit 320 generates the current detection signal IS based on the positive detection voltage V _SNS . Since the output circuit 320 has a high impedance input, the charge of the capacitor C31 is held during the second phase φ2, and therefore the voltage V _n1 is constant.

Figure 4 is an operational waveform diagram of the current detection circuit 300 in Figure 1. The high-side transistor 402 and the low-side transistor 404 are turned on complementarily. In reality, a dead time is inserted between the on interval of the high-side transistor 402 and the on interval of the low-side transistor 404, but this is omitted here.

Let us focus on the on-period (low-side on-period) T _L of the low-side transistor 404. The voltage V _SW of the switching line SW is a negative voltage as described above.
V _SW =-R _{ON_L} ×I _L
It changes according to.

When the low-side on section T _L is entered, the current detection circuit 300 enters the first phase φ1. At this time, the voltage V _n1 at the first end n1 of the capacitor C31 becomes 0V, and the voltage V _n2 at the second end n2 becomes a negative voltage equal to the voltage V _SW of the switching line SW. The voltage across the capacitor C31 is equal to the absolute value of the switching voltage V _SW .

At the sensing timing (time _t0 ), the phase is switched to the second phase φ2. In the second phase φ2, both ends of the capacitor C31 are in high impedance, so that the charge is stored. Therefore, during the second phase φ2, the voltage between both ends is maintained at a voltage level equal to the absolute value _VSW(SH) of the switching voltage _VSW at time _t0 . In the second phase φ2, the second terminal n2 is 0V, so that the voltage _Vn1 of the first terminal n1 is a positive voltage |VSW _(SH) | indicating the absolute value of the switching voltage _VSW(SH) , and this voltage _Vn1 is output as the detection voltage _VSNS .

The above is the operation of the current detection circuit 300. According to this current detection circuit 300, by using a combination of the capacitor C31 and the switch circuit 310, the voltage drop of the low-side transistor 404 can be detected as a positive voltage, and a current detection signal IS based on the voltage drop can be generated.

Next, an example of the configuration of the switch circuit 310 will be described. FIG. 5 is a circuit diagram of an example of the configuration of the switch circuit 310 of FIG. 1. It includes a plurality of switches SW1 to SW4 and a driver circuit 312. The first switch SW1 is provided between the first end n1 of the capacitor C31 and the ground line GND. The second switch SW2 is provided between the second end n2 of the capacitor C31 and the switching line SW.

The third switch SW3 is provided between the second end n2 of the capacitor C31 and the ground line GND. One end of the fourth switch SW4 is connected to the first end n1 of the capacitor C31, and the other end serves as the output node of the switch circuit 310.

In the first phase φ1, the driver circuit 312 turns on the first switch SW1 and the second switch SW2, and turns off the third switch SW3 and the fourth switch SW4. In the second phase φ2, the driver circuit 312 turns off the first switch SW1 and the second switch SW2, and turns on the third switch SW3 and the fourth switch SW4. A control signal (sense command) indicating the timing of current detection is input to the driver circuit 312 from a higher-level controller (not shown), and the first phase φ1 and the second phase φ2 are switched in response to the control signal.

Fig. 6 is a circuit diagram showing an example of the configuration of the output circuit 320. The output circuit 320 in Fig. 6 is a voltage/current conversion circuit 322, which converts the detection voltage _VSNS from the previous stage into a current detection signal IS that is a current signal.

The voltage/current conversion circuit 322 includes a first transistor M31, a second transistor M32, which are PMOS transistors, a resistor R31, and an operational amplifier OA31. The first transistor M31 has a first end (source) connected to the power supply line V _DD . The second transistor M32 has a first end connected to the power supply line V _DD and a control terminal (gate) connected to the control terminal (gate) of the first transistor M31.

The resistor R31 is provided between the second end (source) of the first transistor M31 and the ground line GND. The operational amplifier OA31 receives the detection voltage _VSNS from the preceding switch circuit 310 and the voltage of the second end (drain) of the first transistor M31, and its output node is connected to the control terminal (gate) of the first transistor M31. The current flowing through the second transistor M32 becomes the current detection signal IS.

Since an imaginary short occurs in the operational amplifier OA31, the voltage of the connection node between the resistor R31 and the first transistor M31 becomes equal to the detection voltage V _SNS . Therefore, a current of V _SNS /R31 flows through the resistor R31, and this current also flows through the first transistor M31. The current I _M31 flowing through the first transistor M31 is copied by the second transistor M32, or amplified as necessary, and output. The current I _M32 flowing through the second transistor M32 is proportional to the detection voltage V _SNS .

Next, we will explain the uses of the current detection circuit 300.

7 is a circuit diagram of the DC/DC converter 100. The DC/DC converter 100 is a synchronous rectification type step-down converter (Buck converter) that steps down the input voltage _VIN at the input terminal P1 and supplies power to a load connected to the output terminal P2.

It comprises a switching transistor M1, a synchronous rectifier transistor M2, an inductor L1, an output capacitor C1, a bootstrap capacitor C2, and a control circuit 200. The control circuit 200 is a functional IC integrated on a single semiconductor substrate.

The high-side gate (HG) pin of the control circuit 200 is connected to the gate of the switching transistor M1, and the low-side gate (LG) pin is connected to the gate of the synchronous rectification transistor M2. The switching pin SW is connected to a switching line connecting the switching transistor M1 and the synchronous rectification transistor M2. The ground pin (GND) is grounded. The bootstrap (VB) pin is connected to a bootstrap capacitor C2. The feedback (FB) pin receives a feedback signal according to the output of the DC/DC converter 100. In the case of a constant voltage output DC/DC converter 100, the feedback signal is a signal according to the output voltage V _OUT of the DC/DC converter 100. In the case of a constant current output DC/DC converter 100, the feedback signal is a signal according to the output current I _OUT of the DC/DC converter 100.

The control circuit 200 includes a pulse modulator 202, a current detection circuit 204, a level shifter 206, a high-side driver 208, a low-side driver 210, and a diode D1. The diode D1 forms a bootstrap circuit together with an external bootstrap capacitor C2, and the cathode of the diode D1 is connected to the VB pin, and a constant voltage _VREG is applied to the anode of the diode D1. The switching transistor M1 may be a P-channel/PNP type transistor, in which case the bootstrap circuit is omitted.

The switching transistor M1 and the synchronous rectification transistor M2 may be integrated into the control circuit 200.

The pulse modulator 202 generates a pulse signal that is pulse modulated so that the feedback signal _VFB at the feedback pin FB approaches a target level. The control method and configuration of the pulse modulator 202 are not particularly limited, and any known technology may be used. For example, the pulse modulator 202 may be a pulse width modulator that feedback controls the duty cycle of the pulse signal so that the feedback signal _VFB approaches its target signal _VREF . Alternatively, the pulse modulator 202 may be a pulse frequency modulator.

The pulse modulator 202 may also include a voltage mode controller, or a peak current mode or average current mode controller. Alternatively, the pulse modulator 202 may be in peak current mode.

The pulse modulator 202 may also include a controller for ripple control, and more specifically, may include a controller for a hysteresis control (Bang-Bang control) method, a bottom detection fixed on-time method, or a peak detection fixed off-time method.

The pulse modulator 202 generates a high-side control signal HIN and a low-side control signal LIN based on the pulse signal generated internally.

The level shifter 206 level-shifts the high-side control signal HIN. The high-side driver 208 drives the switching transistor M1 in response to the level-shifted high-side control signal HIN'. The low-side driver 210 drives the synchronous rectification transistor M2 in response to the low-side control signal LIN.

The current detection circuit 204 detects the current flowing through the synchronous rectifier transistor M2 and generates a current detection signal IS. If the pulse modulator 202 includes a current-mode controller, the current detection signal IS is reflected in the duty cycle and frequency of the pulse signal. Alternatively, the current detection signal IS may be used to detect a light load state or an overcurrent.

The current detection circuit 204 is configured using the architecture of the current detection circuit 300 described above. The switching transistor M1 and the synchronous rectification transistor M2 can correspond to the high-side transistor 402 and the low-side transistor 404 in FIG. 1. The pulse modulator 202 generates a current sense command SNS at an appropriate timing during the period when the synchronous rectification transistor M2 is on, in synchronization with the switching of the switching transistor M1 and the synchronous rectification transistor M2. In response to the current sense command SNS, the current detection circuit 204 switches between the first phase φ1 and the second phase φ2 to generate the current detection signal IS.

8 is a diagram showing an example of an electronic device 700 including a DC/DC converter 100. The electronic device 700 is, for example, a battery-driven device such as a mobile phone terminal, a digital camera, a digital video camera, a tablet terminal, or a portable audio player. The electronic device 700 includes a housing 702, a battery 704, a microprocessor 706, and a DC/DC converter 100. The DC/DC converter 100 receives a battery voltage V _BAT (=VIN) from the battery 704 at its input terminal, and supplies an output voltage V _OUT to the microprocessor 706 connected to its output terminal.

Alternatively, the DC/DC converter 100 can be used in electrical equipment installed in an automobile, or as a battery charger, etc.

The embodiments are merely examples, and those skilled in the art will understand that various modifications are possible in the combination of each component and each processing process, and that such modifications are also within the scope of this disclosure or the present invention. The following describes such modifications.

The application of the current detection circuit 300 is not limited to DC/DC converters, but can be widely applied to current detection in push-pull switching circuits that include high-side and low-side transistors.

For example, the current detection circuit 300 can be used to detect the current of a low-side transistor in a three-phase inverter or H-bridge circuit that uses a motor as a load. Figure 9 is a circuit diagram of the motor drive system 500.

Motor 502 is a three-phase DC motor and includes a three-phase coil. Inverter 504 is a three-phase inverter connected to motor 502 and includes three legs, each of which includes a high-side transistor MH and a low-side transistor ML.

The current detection circuit 506 detects the current of each phase. The controller 508 generates a control signal Sctrl based on the current detected by the current detection circuit. The driver 510 drives the inverter 504 based on the control signal Sctrl.

The current detection circuit 300 described above can be used to detect the current of the low-side transistor ML in the current detection circuit 506.

The embodiments merely illustrate the principles and applications of this disclosure or the present invention, and many modifications and changes in arrangement are permitted to the embodiments without departing from the spirit of the present invention as defined in the claims.

400 Switching circuit IN Input line SW Switching line GND Ground line 402 High side transistor 404 Low side transistor 410 Driver circuit 300 Current detection circuit C31 Capacitor 310 Switch circuit 312 Driver circuit SW1 First switch SW2 Second switch SW3 Third switch SW4 Fourth switch 320 Output circuit 322 Voltage/current conversion circuit M31 First transistor M32 Second transistor M33 Third transistor R31 Resistor OA31 Operational amplifier 100 DC/DC converter 102 Driver 104 Current detection circuit M1 Switching transistor M2 Synchronous rectifier transistor L1 Inductor C1 Output capacitor C2 Bootstrap capacitor P1 Input terminal P2 Output terminal 200 Control circuit 202 Pulse modulator 204 Current detection circuit 206 Level shifter 208 High-side driver 210 Low-side driver 700 Electronic device 702 Housing 704 Battery 706 Microprocessor 500 Motor drive system 502 Motor 504 Inverter 506 Current detection circuit 508 Controller 510 Driver

Claims (11)

A control circuit for a synchronous rectification type step-down DC/DC converter including a high-side transistor and a low-side transistor,
a current detection circuit that generates a current detection signal indicative of a current flowing through the low-side transistor while the low-side transistor is on;
a pulse modulator that generates a pulse signal for controlling the high-side transistor and the low-side transistor based on the current detection signal;
Equipped with
The current detection circuit includes:
A capacitor;
(i) in a first phase, a switch circuit that connects a first end of the capacitor to a ground line and connects a second end of the capacitor to a switching line to which the high-side transistor and the low-side transistor are connected, and (ii) in a second phase, a switch circuit that sets the first end of the capacitor to high impedance and connects the second end of the capacitor to the ground line;
an output circuit having a high impedance input and outputting a current detection signal based on a voltage generated at the first end of the capacitor in the second phase;
A control circuit comprising: The switch circuit includes:
a first switch that is provided between the first end of the capacitor and the ground line and is turned on in the first phase;
a second switch provided between the second end of the capacitor and the switching line, the second switch being turned on in the first phase;
a third switch that is provided between the second end of the capacitor and the ground line and is turned on in the second phase;
a fourth switch having one end connected to the first end of the capacitor and turned on in the second phase;
The control circuit of claim 1 , comprising: The output circuit includes:
3. The control circuit according to claim 1, further comprising a voltage/current conversion circuit for converting a voltage generated at the first end of the capacitor in the second phase into a current signal. The voltage/current conversion circuit includes:
a first transistor having a first end connected to a power supply line;
a second transistor having a first end connected to the power supply line and a control terminal connected to the control terminal of the first transistor;
a resistor provided between the second end of the first transistor and a ground line;
an operational amplifier that receives a voltage generated at the first end of the capacitor and a voltage at the second end of the first transistor and has an output node connected to the control terminal of the first transistor;
4. The control circuit according to claim 3, further comprising: a first transistor connected to said second transistor; A control circuit according to any one of claims 1 to 4, which is integrated on a single semiconductor substrate. A synchronous rectification type step-down DC/DC converter equipped with a controller according to any one of claims 1 to 5. A current detection circuit for use with a push-pull switching circuit including a high-side transistor and a low-side transistor, detecting a source current flowing through the low-side transistor, comprising:
A capacitor;
(i) in a first phase, a switch circuit that connects a first end of the capacitor to a ground line and connects a second end of the capacitor to a switching line to which the high-side transistor and the low-side transistor are connected, and (ii) in a second phase, a switch circuit that sets the first end of the capacitor to high impedance and connects the second end of the capacitor to the ground line;
an output circuit having a high impedance input and outputting a current detection signal based on a voltage generated at the first end of the capacitor in the second phase;
A current detection circuit comprising: The switch circuit includes:
a first switch that is provided between the first end of the capacitor and the ground line and that is turned on in the first phase;
a second switch provided between the second end of the capacitor and the switching line, the second switch being turned on in the first phase;
a third switch that is provided between the second end of the capacitor and the ground line and is turned on in the second phase;
a fourth switch having one end connected to the second end of the capacitor and turned on in the second phase;
8. The current sensing circuit of claim 7, comprising: The output circuit includes:
9. The current detection circuit according to claim 7, further comprising a voltage/current conversion circuit that converts a voltage generated at the first end of the capacitor in the second phase into a current signal. The voltage/current conversion circuit includes:
a first transistor having a first end connected to a power supply line;
a second transistor having a first end connected to the power supply line and a control terminal connected to the control terminal of the first transistor;
a resistor provided between the second end of the first transistor and a ground line;
an operational amplifier that receives a voltage generated at the first end of the capacitor and a voltage at the second end of the first transistor and has an output node connected to the control terminal of the first transistor;
10. The current detection circuit according to claim 9, further comprising: a first transistor connected to said first transistor; A current detection circuit according to any one of claims 7 to 10, which is integrated on a single semiconductor substrate.

Images